Copper porous body, copper porous composite member, method for producing copper porous body, and method for producing copper porous composite member

ABSTRACT

This porous copper body includes: a skeleton which is formed of a sintered body of a plurality of copper fibers and has a three-dimensional network structure, wherein the copper fibers forming the skeleton consist of copper or a copper alloy, and the copper fibers have a diameter R in a range of 0.01 mm to 1.0 mm, a ratio L/R of a length L to the diameter R in a range of 4 to 200, and a circularity of a cross section orthogonal to a length direction in a range of 0.2 to 0.9, and the porous copper body has a porosity of 50% to 95%.

TECHNICAL FIELD

The present invention relates to a porous copper body (copper porousbody) consisting of copper or a copper alloy, a porous copper compositemember (copper porous composite member) in which the porous copper bodyis bonded to a member main body, a method for producing the porouscopper body, and a method for producing the porous copper compositemember.

The present application claims priority on Japanese Patent ApplicationNo. 2017-006749 filed on Jan. 18, 2017, the content of which isincorporated herein by reference.

BACKGROUND ART

The porous copper sintered body and the porous copper composite memberare used, for example, as electrodes and current collectors in variousbatteries, heat exchanger components such as heat pipes, silencingcomponents, filters, impact-absorbing components, and the like.

For example, Patent Document 1 proposes a heat transfer member in whicha porous copper body having a three-dimensional network structure isintegrally adhered to a conductive metal member main body.

As a method for producing a metal sintered body (porous copper body)having the three-dimensional network structure, Patent Document 1discloses a method in which a pressure sensitive adhesive is applied toa skeleton of a three-dimensional network structure (for example,synthetic resin foam having open cells such as urethane foam andpolyethylene foam, and a natural fiber cloth, a man-made fiber cloth,and the like) made of a material burned off by heating, and a metalpowder material is adhered to obtain a formed body, and the formed bodyis used, and a method in which a metal powder material is plowed in amaterial (for example, pulp or wool fiber) made of a raw material burnedoff by heating and capable of forming a three-dimensional networkstructure to obtain a sheet-like formed body, and the sheet-like formedbody is used.

As described in Patent Document 1, in the case of forming a metalsintered body (porous copper sintered body) by using a metal powderysubstance, the shrinkage rate at the time of sintering is large.Therefore, there is a problem in that it is difficult to obtain a porouscopper sintered body which has high strength and high porosity.

Therefore, for example, as described in Patent Documents 2 and 3, aporous copper body in which copper fibers consisting of copper or acopper alloy are used as a sintering raw material is proposed.

Patent Document 2 discloses a method for obtaining a porous copper bodyby electrically heating copper fibers under pressure.

Patent Document 3 discloses a method for obtaining a porous copper bodyby heating copper fibers at 800° C. in air and then heating the copperfibers at 450° C. in a hydrogen atmosphere.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Unexamined Patent Application, First    Publication No. H8-145592-   Patent Document 2: Japanese Patent No. 3735712-   Patent Document 3: Japanese Unexamined Patent Application, First    Publication No. 2000-192107

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the above-described porous copper body, high strength is requiredtogether with high porosity and an open cell structure.

In Patent Document 2, there is a problem in that the porosity decreasesbecause it is necessary to perform electrical sintering under pressurein order to sufficiently bond the copper fibers to each other. Inaddition, there is a problem in that a shape of a forming die to be usedat the time of sintering is limited because it is necessary for uniformpressure to be applied.

Further, in Patent Document 3, since the heating is carried out in air,there are concerns that the oxygen concentration in the copper fiberswill increase, or thereafter, voids will be generated when heating inthe hydrogen atmosphere and the strength of the porous copper body willdecrease.

The invention has been made in consideration of the above-describedcircumstances, and an object thereof is to provide a porous copper bodywhich has high porosity and sufficient strength, a porous coppercomposite member in which the porous copper body is bonded to a membermain body, a method for producing a porous copper body, and a method forproducing a porous copper composite member.

Solutions for Solving the Problems

To solve the above-described problem and to accomplish theabove-described object, the porous copper body according to theinvention includes a skeleton which is formed of a sintered body of aplurality of copper fibers and has a three-dimensional networkstructure, wherein the copper fibers forming the skeleton consist ofcopper or a copper alloy, and the copper fibers have a diameter R in arange of 0.01 mm to 1.0 mm, a ratio L/R of a length L to the diameter Rin a range of 4 to 200, and a circularity of a cross section orthogonalto a length direction in a range of 0.2 to 0.9, and the porous copperbody has a porosity of 50% to 95%.

According to the porous copper body having this configuration, withregard to the copper fibers forming the skeleton, the diameter R is in arange of 0.01 mm to 1.0 mm and the ratio L/R of the length L to thediameter R is in a range of 4 to 200. Therefore, it is possible tosecure sufficient voids between the copper fibers; and thereby, theporosity can be in a range of 50% to 95%.

The diameter R is a value that is calculated on the basis of across-sectional area A of each fiber, and is defined by the followingexpression on the assumption that the cross-sectional shape is a perfectcircle regardless of an actual cross-sectional shape.

R=(A/π)^(1/2)×2

In addition, in the invention, the circularity of the cross sectionorthogonal to the length direction of the copper fibers forming theskeleton is defined. The circularity C is expressed by the followingexpression when a cross-sectional area of the copper fiber isrepresented as A and a circumferential length of the cross section ofthe copper fiber is represented as Q.

Circularity C=(4πA)^(0.5) /Q

In the case where the cross-sectional shape is a perfect circle, thecircularity C becomes 1. In the case where the cross-sectional shape isa concave polygon such as a star shape, a rectangle having a largeaspect ratio, or the like, the circularity C approaches 0.

In the present invention, the circularity of the cross section of eachof the copper fibers forming the skeleton is in a range of 0.2 to 0.9.Therefore, when laminating the copper fibers, there are many portionswhere the copper fibers are in surface contact with each other.Therefore, it is possible to secure a contact area between the laminatedcopper fibers; and thereby, bonding strength between the copper fiberscan be improved, and in addition, voids can be secured between thecopper fibers and the porosity can be increased.

Accordingly, it is possible to provide a porous copper body having highporosity and sufficient strength.

The porous copper composite member according to the invention includes:a bonded body of a member main body and a porous copper body including askeleton of a three-dimensional network structure, wherein the porouscopper body is the above-described porous copper body.

According to the porous copper composite member having thisconfiguration, since it is configured to include the bonded body of aporous copper body having high porosity and excellent strength and themember main body, it is possible to provide a porous copper compositemember having excellent characteristics.

In the porous copper composite member according to the invention, it ispreferable that a bonded surface of the member main body bonded to theporous copper body consists of copper or a copper alloy, and a bondedportion between the porous copper body and the member main body is asintered layer.

In this case, since the bonded portion between the porous copper bodyand the member main body is the sintered layer, the porous copper bodyand the member main body are strongly bonded to each other, and thus theporous copper composite member can have excellent strength.

In addition, the method for producing a porous copper body according tothe invention is the method for producing a porous copper body includinga skeleton which is formed of a sintered body of a plurality of copperfibers and has a three-dimensional network structure, and the methodincludes: a copper fiber lamination step of laminating the copperfibers, wherein with regard to the copper fibers, a diameter R is in arange of 0.01 mm to 1.0 mm, a ratio L/R of a length L to the diameter Ris in a range of 4 to 200, and a circularity of a cross sectionorthogonal to a length direction is in a range of 0.2 to 0.9; and asintering step of sintering the plurality of laminated copper fiberstogether.

According to the method for producing the porous copper body having thisconfiguration, with regard to the copper fibers, the diameter R is in arange of 0.01 mm to 1.0 mm, the ratio L/R of the length L to thediameter R is in a range of 4 to 200, and the circularity of the crosssection orthogonal to the length direction is in a range of 0.2 to 0.9.Therefore, a contact area between the copper fibers is secured, and thusit is possible to obtain a porous copper body having high strength. Inaddition, it is possible to secure voids between the copper fibers, andthus it is possible to obtain a porous copper body having high porosity.

The method for producing a porous copper composite member according tothe invention is the method for producing a porous copper compositemember including a bonded body of a member main body and a porous copperbody including a skeleton of a three-dimensional network structure, andthe method includes: a bonding step of bonding the above-describedporous copper body and the member main body to each other.

According to the method for producing the porous copper composite memberhaving this configuration, the porous copper body produced by theabove-described method for producing a porous copper body, thus it ispossible to obtain a porous copper composite member excellent incharacteristics such as strength and the like. Examples of the membermain body include a plate, a rod, a tube, and the like.

In the method for producing a porous copper composite member of theinvention, it is preferable that a bonded surface of the member mainbody, to which the porous copper body is bonded, consists of copper or acopper alloy, and the porous copper body and the member main body arebonded to each other by sintering.

In this case, the member main body and the porous copper body can beintegrated with each other through the sintering, and thus it ispossible to produce a porous copper composite member excellent instability of characteristics.

Effects of the Invention

According to the invention, it is possible to provide a porous copperbody which has high porosity and sufficient strength, a porous coppercomposite member in which this porous copper body is bonded to a membermain body, a method for producing a porous copper body, and a method forproducing a porous copper composite member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged schematic view of a porous copper body accordingto a first embodiment of the invention.

FIG. 2 is a graph showing circularity of a regular polygon.

FIG. 3 is a graph showing circularity of a rectangle.

FIG. 4 is a schematic explanatory view of a cross-sectional shape of oneof the copper fibers forming a skeleton of the porous copper body shownin FIG. 1.

FIG. 5 is a flowchart showing an example of a method for producing theporous copper body shown in FIG. 1.

FIG. 6 is a view showing production steps of producing the porous copperbody shown in FIG. 1.

FIG. 7 is a view showing an external appearance of a porous coppercomposite member according to a second embodiment of the invention.

FIG. 8 is a flowchart showing an example of a method for producing theporous copper composite member shown in FIG. 7.

FIG. 9 is an external view of a porous copper composite member accordingto one of other embodiments of the invention.

FIG. 10 is an external view of a porous copper composite memberaccording to one of other embodiments of the invention.

FIG. 11 is an external view of a porous copper composite memberaccording to one of other embodiments of the invention.

FIG. 12 is an external view of a porous copper composite memberaccording to one of other embodiments of the invention.

FIG. 13 is an external view of a porous copper composite memberaccording to one of other embodiments of the invention.

FIG. 14 is an external view of a porous copper composite memberaccording to one of other embodiments of the invention.

FIG. 15 is an external view of a porous copper composite memberaccording to one of other embodiments of the invention.

FIG. 16 is an external view of a porous copper composite memberaccording to one of other embodiments of the invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, a description will be provided for a porous copper body, aporous copper composite member, a method for producing the porous copperbody, and a method for producing the porous copper composite memberaccording to embodiments of the invention with reference to theaccompanying drawings.

First Embodiment

First, a description will be provided of a porous copper body 10according to a first embodiment of the invention with reference to FIG.1 to FIG. 6.

As shown in FIG. 1, the porous copper body 10 according to thisembodiment includes a skeleton 12 in which a plurality of copper fibers11 are sintered.

In the porous copper body 10 of this embodiment, a porosity P is in arange of 50% to 95%. The porosity P is calculated by the followingexpression.

P(%)=(1−(m/(V×D _(T))))×100

-   -   m: Mass (g) of porous copper body 10    -   V: Volume (cm³) of porous copper body 10    -   D_(T): True density (g/cm³) of copper fibers 11 forming porous        copper body 10

Further, in the porous copper body 10 according to this embodiment, arelative tensile strength S/D_(A) (N/mm²) obtained by normalizing atensile strength S (N/mm²) with an apparent density ratio D_(A) is 10.0or greater. The apparent density ratio D_(A) is calculated by thefollowing expression.

D _(A) =m/(V×D _(T))

The copper fibers 11 forming the skeleton 12 consist of copper or acopper alloy, and a diameter R is in a range of 0.01 mm to 1.0 mm, and aratio L/R of a length L to the diameter R is in a range of 4 to 200. Inthis embodiment, the copper fibers 11 consist of, for example, C1020(oxygen-free copper).

Furthermore, in this embodiment, the copper fiber 11 is subjected toshape imparting such as twisting and bending. In addition, in the porouscopper body 10 according to this embodiment, an apparent density ratioD_(A) is 0.50 or less of a true density D_(T) of the copper fibers 11. Ashape of the copper fiber 11 is an arbitrary shape such as a linearshape and a curved shape as long as the apparent density ratio D_(A) is0.50% or less of the true density D_(T) of the copper fibers 11.However, in the case where copper fibers 11 in which at least a partthereof is subjected to a predetermined shape imparting processing suchas twisting processing and bending processing are used, it is possibleto form voids between the copper fibers 11 in a three-dimensional andisotropic shape. As a result, it is possible to improve isotropy invarious characteristics such as strength, heat transfer characteristics,and conductivity of the porous copper body 10.

The copper fibers 11 are produced through adjustment into apredetermined diameter R by a drawing method, a coil cutting method, awire cutting method, a melting spraying method, and the like, and lengthadjustment for satisfying predetermined L/R by cutting.

The diameter R is a value that is calculated on the basis of across-sectional area A of each fiber, and is defined by the followingexpression on the assumption that the cross-sectional shape is a perfectcircle regardless of an actual cross-sectional shape.

R=(A/π)^(1/2)×2

In the copper fibers 11 forming the skeleton 12, the circularity C of across section orthogonal to the length direction is in a range of 0.2 to0.9.

The circularity C is defined by the following expression when across-sectional area of the copper fiber 11 is represented as A and acircumferential length of the cross section of the copper fiber 11 isrepresented as Q.

Circularity C=(4πA)^(0.5) /Q

In the case of a perfect circle, the circularity C is 1. As thecircumferential length Q is longer than the cross-sectional area A, thecircularity C becomes smaller. Accordingly, in the case where the crosssection has a shape of a concave polygon such as a star shape or in thecase where the cross section has a shape having a large aspect ratio,the circularity C decreases.

FIG. 2 shows a graph showing the circularity C of the regular polygon,and FIG. 3 shows a graph showing a relationship between the aspect ratioand the circularity C in a rectangular cross section.

As shown in FIG. 2, in the case of a regular polygon, when thecircularity C is in a range of 0.2 to 0.9, it is an equilateral triangleand a square.

In addition, in the case of a rectangular shape, when the circularity Cis in a range of 0.2 to 0.9, it is the case where the aspect ratio (longside length/short side length) is 80 or less.

In this embodiment, as shown in FIG. 4, the copper fibers 11 forming theskeleton 12 are assumed to have a substantially triangularcross-sectional shape.

In the case where the diameter R of the copper fiber 11 is less than0.01 mm, a bonding area between the copper fibers 11 is small, and thusthere is a concern that sintering strength may be deficient. On theother hand, in the case where the diameter R of the copper fiber 11 isgreater than 1.0 mm, the number of contact points at which the copperfibers 11 come into contact with each other is deficient, and thus thereis a concern that the sintering strength may also be deficient.

In view of these, in this embodiment, the diameter R of the copper fiber11 is set to be in a range of 0.01 mm to 1.0 mm. Furthermore, it ispreferable that the lower limit of the diameter R of the copper fiber 11is set to be 0.03 mm or greater, and the upper limit of the diameter Rof the copper fiber 11 is set to be 0.5 mm or less so as to furtherimprove the strength.

In addition, in the case where the ratio L/R of the length L to thediameter R of the copper fiber 11 is less than 4, when the copper fibers11 are laminated, it is difficult to set the bulk density D_(P) to be50% or less of the true density DT of the copper fibers 11, and thusthere is a concern that it is difficult to obtain the porous copper body10 having high porosity P. On the other hand, in the case where theratio L/R of the length L to the diameter R of the copper fiber 11 isgreater than 200, when the copper fibers 11 are laminated, it isdifficult to uniformly disperse the copper fibers 11, and thus there isa concern that it is difficult to obtain the porous copper body 10having a uniform porosity P.

In view of these, in this embodiment, the ratio L/R of the length L tothe diameter R of the copper fiber 11 is set to be in a range of 4 to200. Furthermore, it is preferable that the lower limit of the ratio L/Rof the length L to the diameter R of the copper fiber 11 is set to be 10or greater so as to further improve the porosity P. In addition, it ispreferable that the upper limit of the ratio L/R of the length L to thediameter R of the copper fiber 11 is set to be 100 or less so as toobtain the porous copper body 10 having a more uniform porosity P.

Further, in the case where the cross-sectional shape of the copper fiber11 forming the skeleton 12 is a concave polygonal shape such as a starshape and the circularity C is less than 0.2, unevenness of a surface ofthe copper fiber 11 is large and contacting portions between the copperfibers 11 are not secured, and thus there is a concern that the strengthof the porous copper body 10 after sintering may be deficient. Inaddition, in the case where, in the cross-sectional shape of the copperfiber 11 forming the skeleton 12, the aspect ratio between the long sideand the short side becomes large and the circularity C becomes less than0.2, the copper fiber 11 becomes a foil shape, and thus it becomesdifficult to form voids between the copper fibers 11 at the time offilling; and as a result, there is a concern that the porosity P of theporous copper body 10 after sintering may decrease.

On the other hand, in the case where the circularity C of the crosssection of the copper fiber 11 forming the skeleton 12 is greater than0.9, the cross-sectional shape approaches a perfect circle, and thus thecontacting portions between the copper fibers 11 at the time of fillingare in point contact. Therefore, bonding strength of the copper fibers11 at each contact point decreases, and as a result, there is a concernthat the strength of the porous copper body 10 after sintering may bedeficient.

In a three-dimensional network structure formed by bonding metal fiberstogether, since tensile strength is strongly influenced by portionswhere bonding strength between fibers is weak, it is considered thatwhen a contact point at which bonding strength is weak is formed bypoint contact, destruction progresses from this contact point as astarting point at the time of tension.

In view of these, in this embodiment, the circularity C of the crosssection of the copper fiber 11 forming the skeleton 12 is set to be in arange of 0.2 to 0.9. Furthermore, it is preferable that the lower limitof the circularity C of the cross section of the copper fiber 11 formingthe skeleton 12 is set to be 0.3 or greater, and the upper limit thereofis set to be 0.85 or less so as to further improve the porosity P andstrength.

Next, a description will be provided of a method for producing theporous copper body 10 according to this embodiment with reference to theflowchart in FIG. 5, the process diagram of FIG. 6, and the like.

First, as shown in FIG. 6, the above-described copper fibers 11 aredistributed from a distributor 31 toward an inside of a graphitecontainer 32 to bulk-fill the graphite container 32. Thereby, the copperfibers 11 are laminated (copper fiber lamination step S01).

In the copper fiber lamination step S01, a plurality of the copperfibers 11 are laminated so that a bulk density D_(P) after the fillingbecomes 40% or less of the true density D_(T) of the copper fibers 11.Furthermore, in this embodiment, shape imparting processing such astwisting processing and bending processing is carried out with respectto copper fibers 11, and thus it is possible to secure athree-dimensional and isotropic voids between the copper fibers 11during lamination.

Next, the copper fibers 11, with which the graphite container 32 isbulk-filled, are charged into an atmosphere furnace 33 and sintered byheating in a reducing atmosphere, an inert gas atmosphere, or a vacuumatmosphere (sintering step S02).

Heating conditions of the sintering step S02 in this embodiment are asfollows. Specifically, a holding temperature is set to be in a range of500° C. to 1050° C., and holding time is set to be in a range of 5minutes to 600 minutes.

In the case where the holding temperature in the sintering step S02 islower than 500° C., there is a concern that a sintering rate is slow andthus sintering may not proceed sufficiently. On the other hand, in thecase where the holding temperature in the sintering step S02 is higherthan 1050° C., there is a concern that heating may be performed at atemperature near the melting point of copper, and thus a decrease instrength and porosity P may occur.

In view of these, in this embodiment, the holding temperature in thesintering step S02 is set to be in a range of 500° C. to 1050° C.Furthermore, in the sintering step S02, it is preferable that the lowerlimit of the holding temperature is set to be 600° C. or higher, and theupper limit of the holding temperature is set to be 1000° C. or lower soas to reliably perform the sintering of the copper fibers 11.

In addition, in the case where the holding time in the sintering stepS02 is shorter than 5 minutes, there is a concern that a sintering rateis slow and thus sintering may not proceed sufficiently. On the otherhand, in the case where the holding time in the sintering step S02 islonger than 600 minutes, there is a concern that thermal shrinkage mayincrease and strength may decrease due to the sintering. In view ofthese, in this embodiment, the holding time in the sintering step S02 isset to be in a range of 5 minutes to 600 minutes. Furthermore, in thesintering step S02, it is preferable that the lower limit of the holdingtime is set to be 10 minutes or longer and the upper limit of theholding time is set to be 180 minutes or shorter so as to reliablyperform the sintering of the copper fibers 11.

Further, as the atmosphere in the sintering step S02, a reducing gassuch as a hydrogen gas, an RX gas, an ammonia decomposition gas, anitrogen-hydrogen mixed gas, and an argon-hydrogen mixed gas may beused, and an inert gas such as a nitrogen gas and an argon gas may alsobe used. Further, a vacuum atmosphere of 100 Pa or less may also beused.

The sintering progresses at the contacting portion between the copperfibers 11 through the sintering step S02, and the copper fibers 11 arebonded to each other to form a skeleton 12.

In this embodiment, since the sintering step S02 is carried out in areducing atmosphere, an inert atmosphere, and a vacuum atmospherewithout pressurizing as described above, a bulk shape and a surfaceshape of the copper fiber 11 do not change significantly, and thecircularity C of the cross section hardly changes before and aftersintering.

According to the porous copper body 10 of this embodiment having thisconfiguration, the copper fibers 11, in which the diameter R is in arange of 0.01 mm to 1.0 mm and the ratio L/R of the length L to thediameter R is in a range of 4 to 200, are sintered to form the skeleton12, and thus sufficient voids are secured between the copper fibers 11,and a shrinkage rate during the sintering can be suppressed to a lowlevel. Accordingly, it is possible to attain high porosity P andexcellent dimensional accuracy.

In this embodiment, since the circularity C of the cross section of thecopper fiber 11 forming the skeleton 12 is in a range of 0.2 to 0.9, thecontact area between the copper fibers 11 is secured and the strengthafter sintering can be enhanced. Also, it is possible to secure voidsbetween the copper fibers 11 and to increase the porosity P.

Accordingly, according to this embodiment, it is possible to provide theporous copper body 10 having a porosity P of 50% to 95% which is highand having excellent strength.

Second Embodiment

Next, a description will be provided of a porous copper composite member100 according to a second embodiment of the invention with reference tothe accompanying drawings.

FIG. 7 shows the porous copper composite member 100 according to thisembodiment. The porous copper composite member 100 includes: a copperplate 120 (member main body) consisting of copper or a copper alloy; anda porous copper body 110 that is bonded to a surface of the copper plate120.

In the porous copper body 110 according to this embodiment, a pluralityof copper fibers are sintered and a skeleton is formed in the samemanner as in the first embodiment. In the porous copper body 110according to this embodiment, the porosity P is in a range of 50% to95%.

The copper fibers forming the skeleton consist of copper or a copperalloy, and a diameter R is in a range of 0.01 mm to 1.0 mm, and a ratioL/R of a length L to the diameter R is in a range of 4 to 200. In thisembodiment, the copper fibers consist of, for example, C1020(oxygen-free copper).

In the copper fibers forming the skeleton, the circularity C of thecross section orthogonal to the length direction is in a range of 0.2 to0.9.

Furthermore, in this embodiment, the copper fibers are subjected toshape imparting such as twisting and bending. In addition, in the porouscopper body 110 according to this embodiment, an apparent density ratioD_(A) is 50% or less of a true density D_(T) of the copper fibers.

Next, a description will be provided of a method for producing theporous copper composite member 100 according to this embodiment withreference to a flowchart in FIG. 8.

First, the copper plate 120 that is a member main body is prepared(copper plate disposing step S100). Next, copper fibers are dispersedand laminated on a surface of the copper plate 120 (copper fiberlamination step S101). In the copper fiber lamination step S101, aplurality of the copper fibers are laminated so that a bulk densityD_(P) becomes 40% or less of the true density D_(T) of the copperfibers.

Next, the copper fibers laminated on the surface of the copper plate 120are sintered to form the porous copper body 110, and the porous copperbody 110 and the copper plate 120 are bonded to each other (sinteringand bonding step S102).

Heating conditions of the sintering and bonding step S102 in thisembodiment are as follows. Specifically, a holding temperature is set tobe in a range of 500° C. to 1050° C., and holding time is set to be in arange of 5 minutes to 600 minutes.

Further, as the atmosphere in the sintering and bonding step S102, areducing atmosphere, an inert gas atmosphere, or a vacuum atmosphere isused. Specifically, a reducing gas such as a hydrogen gas, an RX gas, anammonia decomposition gas, a nitrogen-hydrogen mixed gas, and anargon-hydrogen mixed gas may be used, and an inert gas such as anitrogen gas and an argon gas may also be used. Further, a vacuumatmosphere of 100 Pa or less may also be used.

Through the sintering and bonding step S102, the copper fibers aresintered together to form the porous copper body 110, and the copperfibers and the copper plate 120 are sintered to bond the porous copperbody 110 and the copper plate 120. Accordingly, the porous coppercomposite member 100 according to this embodiment is produced.

According to the porous copper composite member 100 of this embodimenthaving this configuration, since the circularity C of the cross sectionof the copper fiber forming the porous copper body 110 is in a range of0.2 to 0.9, the contact area between the copper fibers is secured andthe strength can be enhanced. Also, it is possible to secure voidsbetween the copper fibers and to increase the porosity P of the porouscopper body 110.

As a result, it is possible to greatly improve various characteristicssuch as heat exchange efficiency, water retention, and evaporationefficiency, when the porous copper composite member 100 is used as aheat exchanging member such as an evaporator or the like.

In addition, in accordance with the method for producing the porouscopper composite member 100 according to this embodiment, the copperfibers are laminated on the surface of the copper plate 120 consistingof copper or a copper alloy, and the sintering and bonding aresimultaneously performed through the sintering and bonding step S102,and thus it is possible to simplify a producing process.

Hereinbefore, description has been given of the embodiments of theinvention, but the present invention is not limited thereto, andapproximate modifications can be made in a range not departing from thetechnical features of the invention.

For example, description has been given of the case where the porouscopper body is produced by using a producing facility shown in FIG. 6.However, the present invention is not limited thereto, and the porouscopper body may be produced by using other producing facilities.

In addition, in this embodiment, description has been given of the casewhere the copper fibers consisting of oxygen-free copper (JIS C1020) areused. However, the present invention is not limited thereto, and purecopper such as phosphorus-deoxidized copper (JIS C1201, C1220) and toughpitch copper (JIS C1100) and a highly conductive copper alloy such as Crcopper (C18200) or Cr—Zr copper (C18150) may also be used.

Further, in the second embodiment, a bonding method in which a sinteredlayer is formed at the bonded portion of the porous copper body and themember main body has been exemplified as a desirable method. However,the present invention is not limited thereto, and the porous copper bodyand the member main body may also be bonded by using a bonding methodsuch as various welding methods (laser welding method and resistancewelding method) or a brazing method in which a brazing material having alow melting temperature is used.

In addition, in the second embodiment, the porous copper compositemember having a structure shown in FIG. 7 is described as an example.However, the present invention is not limited thereto, and it is alsopossible to employ a porous copper composite member having a structureas shown in FIG. 9 to FIG. 14.

For example, as shown in FIG. 9, it is also possible to employ a porouscopper composite member 200 having a structure in which as a member mainbody, a plurality of copper tubes 220 are inserted into a porous copperbody 210.

Alternatively, as shown in FIG. 10, it is also possible to employ aporous copper composite member 300 having a structure in which as amember main body, a copper tube 320 curved in a U-shape is inserted intoa porous copper body 310.

In addition, as shown in FIG. 11, it is also possible to employ a porouscopper composite member 400 having a structure in which a porous copperbody 410 is bonded to an inner peripheral surface of a copper tube 420that is a member main body.

In addition, as shown in FIG. 12, it is also possible to employ a porouscopper composite member 500 having a structure in which a porous copperbody 510 is bonded to an outer peripheral surface of a copper tube 520that is a member main body.

In addition, as shown in FIG. 13, it is also possible to employ a porouscopper composite member 600 having a structure in which porous copperbodies 610 are bonded to an inner peripheral surface and an outerperipheral surface of a copper tube 620 that is a member main body.

In addition, as shown in FIG. 14, it is also possible to employ a porouscopper composite member 700 having a structure in which porous copperbodies 710 are bonded to both surfaces of a copper plate 720 that is amember main body.

Further, as shown in FIG. 15, it is also possible to employ a porouscopper composite member 800 having a structure in which a porous copperbody 810 is bonded to an inner passage of a copper tube 820 that is amember main body.

In addition, as shown in FIG. 16, it is also possible to employ a porouscopper composite member 900 having a structure in which a porous copperbody 910 is bonded to both surfaces of a flat copper tube 920 that is amember main body.

EXAMPLES

Hereinafter, a description will be provided of results of a confirmationexperiment that is carried out to confirm the effects of the invention.

Porous copper sintered bodies having a width of 30 mm, a length of 200mm, and a thickness of 5 mm were produced by using sintering rawmaterials (copper fibers) shown in Table 1 in accordance with theproducing method described in the above-described embodiment. Thediameter R, the ratio L/R of a length L to the diameter R, and thecircularity C of the copper fiber to be used as a raw material weremeasured as follows.

In addition, with regard to the obtained porous copper sintered body,the diameter R, the ratio L/R of the length L to the diameter R, and thecircularity C of the cross section of the copper fiber forming theskeleton, the porosity, and the tensile strength were evaluated asfollows. Evaluation results are shown in Table 2.

(Diameter R of Copper Fiber)

Cross sections orthogonal to the length direction of the copper fibersto be used as a sintering raw material and the copper fibers sampledfrom the porous copper sintered body were respectively observed with anoptical microscope, and equivalent circle diameters (Heywood diameters)R=(A/π)^(0.5)×2 were calculated by image processing using capturedimages, and a simple average value of the equivalent circle diameterswas calculated. This was used as the diameter R of the copper fiber.

(Ratio L/R Between Length L and Diameter R)

The copper fibers to be used as the sintering raw material and thecopper fibers sampled from the porous copper sintered body wererespectively subjected to image analysis using a particle analyzer“Morphologi G3” manufactured by Malvern Instruments Co., Ltd., andthereby, the lengths of the copper fibers were measured, and thecalculated simple average value thereof was used as the length L of thecopper fiber. Using these, the ratio L/R of the length L to the diameterR was calculated.

(Circularity C in Cross Section)

Cross sections orthogonal to the length direction of the copper fibersto be used as the sintering raw material and the copper fibers sampledfrom the porous copper sintered body were respectively observed with anoptical microscope. Simple average values of a cross-sectional area A(mm²) and a circumferential length Q (mm) were calculated by imageprocessing using the captured images, and by using the simple averagevalues thereof, the circularity was calculated in accordance with thefollowing expression.

Circularity C=(4πA)^(0.5) /Q

(Porosity P)

The true density D_(T) (g/cm³) was measured by Archimedes' principleusing the precision balance, and the porosity P was calculated by thefollowing expression. The mass of the porous copper sintered body wasrepresented as m (g), and the volume of the porous copper sintered bodywas represented as V (cm³).

Porosity P(%)=(1−(m/(V×D _(T))))×100

(Tensile Strength)

The obtained porous copper sintered body was processed into a test piecehaving a width of 10 mm, a length of 100 mm, and a thickness of 5 mm,and then the test piece was subjected to a tensile test using universaltesting machines to measure the maximum tensile strength S (N/mm²).Since the maximum tensile strength obtained by the measurement variesdepending on an apparent density, in this example, a value (S/D_(A))obtained by normalizing the maximum tensile strength S with the apparentdensity ratio D_(A) was defined as a relative tensile strength. Theapparent density ratio D_(A) was calculated by the following expression.

D _(A)(N/mm²)=m/(V×D _(T))

TABLE 1 Copper fiber Sintering condition Diameter R Cross-sectionalshape Temperature Time Material (mm) L/R Circularity Remarks Atmosphere(° C.) (min) Present 1 C1100 0.015 5 0.68 Substantially H₂ 900 60Example triangular 2 C1100 0.015 50 0.68 Substantially H₂ 900 60triangular 3 C1100 0.015 100 0.68 Substantially H₂ 900 60 triangular 4C1220 0.15 10 0.25 Star shape N₂—3%H₂ 600 120 5 C1220 0.15 30 0.25 Starshape N₂—3%H₂ 600 120 6 C1220 0.15 150 0.25 Star shape N₂—3%H₂ 600 120 7C1020 1.00 50 0.88 Substantially Ar 1050 10 square 8 C1020 1.00 100 0.88Substantially Ar 1050 10 square 9 C1020 1.00 200 0.88 Substantially Ar1050 10 square 10 C1201 0.30 20 0.38 Rectangular Vacuum 500 500 11 C12010.30 50 0.38 Rectangular Vacuum 500 500 12 C1201 0.30 70 0.38Rectangular Vacuum 500 500 Present 13 C1020 0.50 50 0.51 SubstantiallyRX gas 700 90 Example elliptic 14 C1020 0.50 100 0.51 Substantially RXgas 700 90 elliptic 15 C1020 0.50 150 0.51 Substantially RX gas 700 90elliptic Comparative 1 C1100 0.008 20 0.78 Substantially N₂—3%H₂ 1000 30Example triangular 2 C1100 1.20 100 0.88 Substantially N₂—3%H₂ 1000 30square 3 C1100 0.03 2 0.65 Substantially N₂—3%H₂ 1000 30 elliptic 4C1100 0.10 300 0.85 Substantially N₂—3%H₂ 1000 30 elliptic 5 C1220 0.0840 0.95 Substantially Ar 800 60 circular 6 C1220 0.05 70 0.15 Star shapeAr 800 60 7 C1100 0.30 35 0.18 Rectangular Ar 800 60 * Degree of vacuumwas 100 Pa or less

TABLE 2 Porous copper sintered body Circularity Tensile Diameter ofcross Porosity strength R (mm) L/R section (%) (N/mm²) Present 1 0.015 50.68 54 22.6 Example 2 0.015 50 0.68 78 15.3 3 0.015 100 0.68 84 13.0 40.15 10 0.25 62 20.9 5 0.15 30 0.25 71 14.3 6 0.15 150 0.25 88 10.3 71.00 50 0.88 72 15.8 8 1.00 100 0.88 86 12.8 9 1.00 200 0.88 94 10.0 100.30 20 0.38 55 20.2 11 0.30 50 0.38 76 15.7 12 0.30 70 0.38 80 14.9 130.50 50 0.51 76 14.3 14 0.50 100 0.51 85 11.8 15 0.50 150 0.51 90 10.3Comparative 1 0.008 20 0.78 68 8.7 Example 2 1.20 100 0.88 90 4.6 3 0.032 0.65 46 29.1 4 0.10 300 0.85 95 3.3 5 0.08 40 0.95 81 9.1 6 0.05 700.15 84 6.5 7 0.30 35 0.18 37 30.5

In any of Present Examples 1 to 15 and Comparative Examples 1 to 7, itwas confirmed that there was no significant change in the diameter R,the ratio L/R between length L and diameter R, and the circularity C ofthe cross section between the copper fibers to be used as the sinteringraw material and the copper fibers sampled from the porous coppersintered body.

In Comparative Example 1 in which the diameter R of the copper fiber was0.008 mm and Comparative Example 2 in which the diameter R of the copperfiber was 1.20 mm, it was confirmed that the tensile strengths of theporous copper sintered bodies were low.

In addition, in Comparative Example 3 in which the ratio L/R of thelength L to the diameter R of the copper fiber was 2, the porosity P was46% which was low.

Further, in Comparative Example 4 in which the ratio L/R of the length Lto the diameter R of the copper fiber was 300, the strength was low. Thereason thereof is presumed to be that large voids partially existed andthe strength was greatly reduced locally.

In Comparative Example 5 in which the circularity C of the cross sectionof the copper fiber was 0.95, the tensile strength was low. The reasonthereof is presumed to be that a shape of the cross section was close toa perfect circle and the contact between the copper fibers became apoint contact. In Comparative Example 6 in which the shape of the crosssection of the copper fiber was a star shape and the circularity C was0.15, the tensile strength was low. The reason thereof is presumed to bethat the unevenness of the surface of the copper fiber was large, and acontact point between the copper fibers was reduced.

In Comparative Example 7 in which the shape of the cross section of thecopper fiber was a rectangle and the circularity C was 0.18, theporosity was low. The reason thereof is presumed to be that thecross-sectional shape of the copper fiber became a foil shape and no gapwas formed between the copper fibers.

In contrast, in the porous copper sintered bodies of the presentexamples, the porosity was 50% or more which was high, and the tensilestrength was sufficiently secured.

From the above results, it was confirmed that, according to theinvention, it is possible to provide a high quality porous coppersintered body having high porosity and sufficient strength.

EXPLANATION OF REFERENCE SIGNS

-   -   10, 110: Porous copper body    -   11: Copper fiber    -   12: Skeleton    -   100: Porous copper composite member    -   120: Copper plate (Member main body)

1. A porous copper body comprising: a skeleton which is formed of asintered body of a plurality of copper fibers and has athree-dimensional network structure, wherein the copper fibers formingthe skeleton consist of copper or a copper alloy, and the copper fibershave a diameter R in a range of 0.01 mm to 1.0 mm, a ratio L/R of alength L to the diameter R in a range of 4 to 200, and a circularity ofa cross section orthogonal to a length direction in a range of 0.2 to0.9, and the porous copper body has a porosity of 50% to 95%.
 2. Aporous copper composite member comprising: a bonded body of a membermain body and a porous copper body including a skeleton of athree-dimensional network structure, wherein the porous copper body isthe porous copper body according to claim
 1. 3. The porous coppercomposite member according to claim 2, wherein a bonded surface of themember main body bonded to the porous copper body consists of copper ora copper alloy, and a bonded portion between the porous copper body andthe member main body is a sintered layer.
 4. A method for producing aporous copper body including a skeleton which is formed of a sinteredbody of a plurality of copper fibers and has a three-dimensional networkstructure, the method comprising: a copper fiber lamination step oflaminating the copper fibers, wherein with regard to the copper fibers,a diameter R is in a range of 0.01 mm to 1.0 mm, a ratio L/R of a lengthL to the diameter R is in a range of 4 to 200, and a circularity of across section orthogonal to a length direction is in a range of 0.2 to0.9; and a sintering step of sintering the plurality of laminated copperfibers together.
 5. A method for producing a porous copper compositemember including a bonded body of a member main body and a porous copperbody including a skeleton of a three-dimensional network structure, themethod comprising: a bonding step of bonding the porous copper bodyaccording to claim 1 and the member main body to each other.
 6. Themethod for producing a porous copper composite member according to claim5, wherein a bonded surface of the member main body, to which the porouscopper body is bonded, consists of copper or a copper alloy, and in thebonding step, the porous copper body and the member main body are bondedto each other by sintering.